1. Field of the Invention
The invention relates generally to a unit for treating very densely compacted sewage sludge cake and mixing the sludge with lime or kiln dust and more particularly to a unit for shredding the very densely compacted sewage sludge cake and mixing the shredded sludge cake with lime or kiln dust.
2. Description of Related Art
It is known to mix solidified dewatered sewage sludge cake produced on a filter press with lime and other additives so that the materials can chemically react to neutralize the toxic chemicals present in the sludge. When sewage sludge and other toxic sludges which are compacted to remove water are mixed with lime or kiln dust at a predetermined rate, an exothermic reaction occurs in which the temperature of the mixture of the sludge and the lime increases with the evolution of steam. Neutralization, agglomeration and other changes occur in the sludge within the mixer unit as the exothermic chemical reaction proceeds. As the lime reacts with the aqueous sludge, dehydration of the sludge occurs with an increase in both temperature and pH value. The increase in the temperature and the pH value of the lime sludge mixture destroys bacteria and viruses which are present in the sludge. Hydrates are formed that tend to bind solid particles in the sludge together to form an agglomeration of particles. The reaction product which is discharged from the mixer unit consists of substantially odor-free, dry, friable particles which may be compacted and used as a landfill material.